In a Long-Term Evolution (LTE) system in the related art, a physical-layer data shared channel performs data transmission by taking a Transmission Block (TB) as a basic element. A receiver determines whether or not a current TB is correctly received through a Cyclic Redundancy Check (CRC) of the TB. When the TB is correctly received, the receiver feeds back an Acknowledgement (ACK) message to a sender. When the TB is not correctly received, the receiver feeds back a Negative Acknowledgement (NACK) message to the sender. The sender retransmits data to the receiver after receiving the NACK message, and retransmission is still performed by taking the TB as the element.
When a size of the TB exceeds a specified threshold, the sender is usually required to perform Code Block (CB) segmentation to segment the TB into multiple CBs, and operations of coding, rate matching, CB concatenation and the like are respectively performed on each CB for sending to the receiver.
A CRC is added to each CB before coding, and in addition, each TB also has another CRC. In the LTE system, lengths of the two CRCs are both 24 bit. A CB CRC is used for premature termination of decoding and the CB CRC may also check correctness of a CB. When the CB CRC succeeds in checking, it is indicated that the CB is a correct CB, and when the CB CRC fails in checking, it is indicated that the CB is an incorrect CB.
The TB CRC is used for correctness checking of a received TB. When the TB CRC fails in checking at the receiver, it is indicated that the TB is incorrectly received, and the TB is required to be retransmitted. When a TB includes a relatively larger number of CBs, relatively more resources are occupied by retransmission. For example, as shown in FIG. 1, a TB includes 8 CBs, and only CB2 and CB5 are incorrectly decoded during first transmission. However, during retransmission, the other CBs without errors are also required to be retransmitted. This is because an ACK or NACK of the LTE system in the related art is fed back on a basis of a TB, there is no CB-based A or N feedback and CB-based feedback may cause extremely high uplink A or N feedback overhead.
Packet coding is a technology for coding between data packets, i.e. a process of coding multiple source data packets to generate check data packets. As shown in FIG. 2, a process of generating a check sequence at a position in a check data packet from an information sequence at a position in a source data packet corresponding to the position in the check data packet is packet coding. Each check data packet includes data at a corresponding position in each check sequence. There may be various packet coding methods. For example, check data packets may be generated in a manner of performing an exclusive OR operation on each source data packet, the check data packets may also be generated in a Reed-Solomon coding manner, and the check data packets may further be generated in a fountain code or network coding manner.
In a digital mobile communication system, a coding bit sequence obtained by rate matching is required to be modulated into a digital baseband signal for transmission. In the LTE system, common modulation constellation diagrams include Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), 64 Quadrature Amplitude Modulation (64QAM) and the like. All of these modulation constellation diagrams include some limited discrete constellation points used for representing amplitudes and phases of digital baseband signals, and geographical distances between the constellation points are called as Euclidean distances. When the Euclidean distances between adjacent constellation points are equal and each constellation point is uniformly distributed in a constellation diagram, the modulation constellation diagram is called as a uniform constellation diagram. For example, the modulation constellation diagrams such as QPSK, 16QAM and 64QAM adopted in the LTE system are all uniform constellation diagrams. On the contrary, when Euclidean distances between adjacent constellation points are unequal or each constellation point is nonuniformly distributed in a constellation diagram, the constellation diagram is called as a nonuniform constellation diagram.